And how useful is 500-1200mm if, like most "superzoom" cameras (not the FZ200), the aperture drops to 5.6 and it's backed up by a sensor that requires the use of low ISOs to get a decent picture. At 1200mm, it's hard to keep something in the frame, even if it's standing still. 1/1000 of a second at f5.6 with an ISO of 200 or less requires very good light.

A tripod starts to become a necessary item. Then what happened to the size advantage?

A thousand people can make this sort of argument a thousand times, and all the while superzoom enthusiasts will be running around having fun snapping birds at 1000mm+ EFLs, partly thanks to exceptional image stabilization mechanisms and excellent continuous shooting performance.

It really is possible, otherwise most of us probably would have stopped trying by now.